1. Technical Field of the Invention
The present invention relates generally to ferroelectric devices, and more particularly to ferroelectric devices providing large mechanical output displacements.
2. Discussion of the Related Art
Prior art methods include xe2x80x98Rainbowxe2x80x99 piezoelectric actuators and sensors, more conventional piezoelectric actuators and sensors, and electro-magnetic actuators.
Conventional piezoelectric actuators exhibit limited mechanical displacements. The output of conventional piezoelectric devices is limited by the material""s basically low piezoelectric displacement constant. Thus conventional devices of reasonable thickness (i.e. on the order of a few millimeters) offer only micrometer-sized mechanical output motion. xe2x80x98Rainbowxe2x80x99 actuators, xe2x80x98Mooniesxe2x80x99, unimorphic, and bimorphic piezoelectric actuators exhibit greater mechanical output motion. However even the thinnest ceramic wafers, which exhibit the maximum observed output motion, provide a displacement limited to approximately 1 mm of motion in the z-direction for a device that is 3-4 cm long. Additionally xc2xc mm thick ceramic devices are extremely brittle and fragile so that they are prone to breakage and require special handling. Previous methods of forming xe2x80x98Rainbowxe2x80x99 actuators include an additional chemical reduction process which releases lead vapors from the wafer into the atmosphere.
It is accordingly an object of the present invention to provide a ferroelectric actuator with improved mechanical displacement.
It is another object of the present invention to provide a ferroelectric actuator with improved durability.
It is another object of the present invention to provide a ferroelectric actuator with improved machinability.
It is another object of the present invention to provide a method for producing a ferroelectric actuator which is more environmentally safe than previous methods.
It is yet another object of the present invention to accomplish the foregoing objects in a simple manner.
Additional objects and advantages of the present invention are apparent from the drawings and specification which follow.
According to the present invention, the foregoing and additional objects are obtained by providing a method for producing ferroelectric devices. First, a mold is selected for the device. A prestress layer is placed on the mold and a ferroelectric layer is placed on top of the prestress layer. These layers are bonded together by heating and then cooling the assembled device. The prestress layer may be an adhesive and may include reinforcing material. The ferroelectric layer may be a piezoelectric material, a piezostrictive material or a composite. The ferroelectric layer includes surface electrodes which may be applied by including an electrode layer on either side of the ferroelectric layer prior to heating the assembly.